Refrigerating apparatus



Nov. 28, 1961 J. w. JACOBS 3,010,288

REFRIGERATING APPARATUS Filed Sept. 21, 1959 I N VEN TOR.

v Jame; [d Jacobs BY HIS ATTURNEY United States Patent Ofice 3,010,288 Patented Nov. 28, 1961 3,010,288 REFRIGERATING APPARATUS James W. Jacobs, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Sept. 21, 1959, Ser. No. 841,245 4 Claims. (Cl. 62155) This invention pertains to refrigerating apparatus and especially to systems for defrosting evaporators.

Defrosting evaporators by introducing hot gas has a number of advantages. First, the heat is applied to the innermost part of the evaporator so that the frost and ice is kept between the source of heat and the refrigerated compartment and serves as a shield thereby minimizing the amount of heat reaching the refrigerated compartment. Second, the heat is applied throughout the evaporator and naturally concentrates at the coldest spots where the frost and ice is apt to be the greatest and which require more heat to achieve uniform defrosting. Third, more heat can be applied to make shorter the defrosting period. Fourth, no device such as an electric heater is required to be added to the evaporator.

Despite these advantages, most refrigerators have used other types of defrosting, especially electric heaters which heat from the outside in and must be applied as a separate element to the compressor. When hot gas defrosting has been used, there has been provided a separate bypass line by-passing the condenser with a separate valve which was usually operated by a solenoid under the control of a periodically closed switch. This mechanism and these parts add to the cost of the defrosting system and introduce an additional valve into the system which is subject to leakage. Such leakage can often go unnoticed and reduces the efficiency of the system. The repair of such a valve is relatively diflicult and expensive.

It is an object of this invention to provide a refrigerating system with a hot gas defrosting arrangement which does not require an additional valve or a by-pass line.

It is another object of this invention to provide a refrigerating system with a hot gas defrosting arrangement which cannot reduce the efficiency of the system through leaks.

It is another object of this invention to provide a refrigerating system with a hot gas defrosting arrangement which is inexpensive and reliable.

. These and other objects are attained in the forms shown in the drawing in which a thermostatic automatic expansion valve is used to control the flow of liquid refrigerant from the condenser to the evaporator. For hot gas defrosting, an electric heater in direct heat transfer relation with the thermostatic bulb of the expansion valve is energized sufliciently to heat the bulb to the point at which it will cause wide opening of the expansion valve. This will permit free flow of liquid and gaseous refrigerant from the condenser to the evaporator thus raising the temperature and pressure within the evaporator so that no condensation takes place in the condenser and no refrigeration is accomplished. The evaporator is heated rapidly by the warm liquid and gas received without expansion from the condenser. The motor-compressor unit will operate during this time to pump hot gas into the evaporator to defrost the evaporator. When sufiicient heating has been provided to defrost the evaporator, the heater for the thermostat bulb is deenergized, and the system is returned to normal operation.

Further objects and advantages of the present invertion will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

FIGURE 1 is a diagrammatic representation of a refrigerator and refrigerating system embodying one form of my invention;

FIGURE 2 is a wiring diagram for the refrigerating system shown in FIGURE 1;

FIGURE 3 is a modified form of wiring diagram for the refrigerating system shown in FIGURE 1; and

FIGURE 4 is a second modified wiring diagram for the refrigerating system shown in FIGURE. 1.

Referring now more particularly to FIGURE 1, there is shown a sealed motor-compressor unit 20 which first delivers the compressed refrigerant through a superheat remover coil 22 located beneath a pan 24 which collects defrost water from the collector pan 26 located beneath the refrigerant evaporator 28. The pan 26 is provided with a hose 30 for delivering the defrost water into the pan 24. The normal operation of the compressor supplies sufiicient heat through the superheat removal coil 22 to evaporate the defrost water from the pan 24.

After the superheat is removed from the hot gas, the gas is returned through the conduit 32 to the sealed unit and is then discharged through the conduit 34 into a heat exchanger 36 which exchanges heat with the suction conduit 38. From the heat exchanger 36, the compressed gas flows into the condenser 40 from which condensed refrigerant normally is delivered through a supply conduit 42 to a thermostatic automatic expansion valve 44 provided with a thermostat bulb 46 mounted in heat exchange relation with the outlet portion 48 of the evaporator 28. This outlet portion 48 connects to the suction conduit 38 which extends through the heat exchanger 36 and connects to the suction inlet of the motor-compressor unit 20.

A double ended motor 50 drives a fan 52 which circulates air in heat exchange relation with the condenser 40. The motor 50 also drives a fan 54 which draws air from the below freezing compartment 56 of -a refrigerator cabinet 58 (diagrammatically illustrated) aswell as from an above freezing vegetable drawer 60 and an above freezing compartment 62. This air is circulated over the surfaces of the evaporator 28 in a separate insulated compartment 92 beneath the below freezing compartment 56 and is returned through a duct 64 to the below freezing compartment 56 and through a damper 66 operated by a bellows 68 and a thermostat bulb 70 into the above freezing compartment 62 and the vegetable drawer 60. The below freezing compartment 56 is separated by an insulated wall 57 from the vegetable drawer 60 and the above freezing compartment 62.

The expansion valve 44 normally controls the flow of refrigerant so that the evaporator 28 is maintained at temperatures below freezing. This causes frost to gradually accumulate upon the evaporator 28, and this frost must be removed from time to time since the frost prevents good heat transfer between the refrigerant and the circulating air. To control the operation of the refrigerating system there is provided a thermostat which may include a bellows 72 and a bulb 74 responsive to the temperature of the freezing compartment 56. In the one form of the invention shown in FIGURE 2, under the control of the toggle mechanism 94, the bellows 72 through a connection 76 operates the double throw switch elements 78 and 80. In its high temperature position or condition, the bellows moves the switch elements 78 and 80 to their upper. positions as shown in FIGURE 2. This connects the supply conductor 82 to the motor of the sealed unit 20 which in turn is connected to the second supply conductor 84. The switch member 80 connects the supply conductor 82 through the conductor 86 to the fan motor 50 which in turn also connects to the supply conductor 84. This will cause operation until the freezing compartment 56 is sufliciently cooled.

This cooling will cause the bellows 72 to collapse and move the switch members 78 and 80 to their lowest positions. The upper contact 80 will disconnect the conductor 86 from the supply conductor 82 to stop the operation of the fan motor 50. The switch member 78 will move downwardly so as to connect a heater 88 in series with a thermostat switch 90 and the motor of the motor-compressor unit 20 thereby causing or continuing operation of the motor-compressor unit. The series heater 88 is located in direct heat transfer relation with the thermostat bulb 46 and heats the bulb 46 while the motor-compressor unit is operating. The heating of this bulb forces the thermostatic expansion valve 44 to a wide open position thereby preventing any restriction and opening the conduit 42 for free flow from the condenser 40 into the evaporator 28. Since the fan motor 50 is not operating, there will be no circulation of air over either the condenser 40 or the evaporator 28. This will prevent any effect of the heating of the evaporator 28 upon the air in the freezing compartment 56 or in the vegetable storage drawer 60 or the above freezing compartment 62. Since the fan 52 is not operating, the hot compressed gas delivered from the sealed motor-compressor unit 20 will not be cooled very much and will flow uncondensed through the wide open expansion valve 44 into the evaporator 28 and heat the refrigerant coils of the evaporator 28.

This will melt the frost surrounding the evaporator 28 from the inside. The frost will shield the heated evaporator from the air in the compartment 92 in which the evaporator 28 is located. The frost therefore will minimize the effect of heating of the evaporator 28 for defrosting insofar as its effect upon the air in the compartment 92. Thus, this arrangement will the transmission of heat from the evaporator to the compartment 92 and allow more rapid heating and disposal of the frost. The freezing thermostat 72 is preferably provided with a toggle snap action device 94 which will require a snap action for movement of the contacts 78 and 80. This will provide alternate prolonged refrigerating periods and defrosting periods. It will make the defrosting periods long enough to insure defrosting of the evaporator 28. The switch 90 is operated by a thermostatic switch 96 having a thermostat bulb mounted upon the outlet portion of the evaporator 28 which tends to defrost last. This thermostat 96 is provided with a toggle snap action mechanism and is operably connected to the switch 90 and set to open the switch 90 when this particular portion of this evaporator reaches 36. This switch 90 prevents overheating of the evaporator 28 and yet insures that the entire evaporator will be defrosted every defrosting cycle.

In the form shown in FIGURE 3, a single pole, single throw switch 125 is provided for connecting the supply conductor 127 to the compressor motor 20 which is also connected to the second supply conductor 129. This single pole, single throw switch is connected to and operated by the bellows 72 under the control of the snap action mechanism 94. There is also provided a single pole, double throw switch 131 which during refrigerating periods connects the branch conductor 133, connecting to the switch 125, with the fan motor 50 which is also connected to the supply conductor 129. This double throw switch 131 is normally held in its upper refrigerating position by a time control mechanism 135 connected across the conductor 133 and-the supply conductor 129. Periodically, this time control mechanism 135 moves the double throw switch 131 downwardly to disconnect the fan motor 50 from the conductor 133 and into connection with the switch Mind the heater 88 in a second parallel circuit between the conductor 133 and the supply conductor 129. For a timed period, the switch 131 will be held in its lower position to cause energy to flow through the switch and the heater 88. The switch will normally remain in the closed position during a defrost period initiated by the movement of the switch 131 to its lower position since there will be insufficient cooling of the freezing compartment at this time. The energization of the heater 88 will heat the thermostatbulb 46 sufficiently to cause wide opening of the expansion valve 44 to accomplish the hot gas defrosting as explained previously. This will continue until the bellows 96 responds to a rise of the evaporator 28 to a temperature of 36' under the control of the toggle mechanism 121 causing the opening of the switch 90 and the deenergization of the heater 88 to terminate the defrosting period. After a predetermined time interval, the switch 131 will return to its upper position, and both the motor-compressor unit 20 and the fan motor 50 will cycle according to the closing and opening of the switch 125.

In the form shown in FIGURE 4, the supply conductor 137 connects directly to the sealed motor-compressor unit 20 which is also connected to the second supply conductor 139. A branch conductor 141 connects to the double throw switch 143 which connects the conductor 141 with either the fan motor 50 or the heater 88. The double throw switch 143 is operated by the freezing compartment thermostat 72 under the control of snap action mechanism 94. The sealed motor-compressor unit 20 operates continuously in this system. When refrigeration is required, the switch 143 will be in its upper position providing for operation of the fan motor 50. When refrigeration requirements are satisfied, the thermostat 72 will move the switch 143 to its lower position thereby energizing the heater 88 to heat the thermostat bulb 46 and accomplish the defrosting of the evaporator 28 in the manner previously mentioned. When refrigeration is again required, the double throw switch 143 will be moved to its uppermost position to provide a refrigerating cycle. Thus, this system provides alternate refrigeration and hot gas defrosting.

While the embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. Refrigerating apparatus including refrigerant liquefying means and refrigerant evaporating means, a thermostatic expansion valve including a thermostat bulb for controlling the flow of refrigerant from the liquefying means to the evaporating means for bringing the evaporating means below water freezing temperatures, fan means for circulating air over the surfaces of said evaporating means, and thermostatic means responsive to the temperature of the circulating air for stopping the fan means, and means for heating the thermostat bulb to open wide the expansion valve for unrestricted flow of fluid from the liquefying means to the evaporating means coincidentally to the stopping of said fan means to raise the temperature of the evaporating means above freezing for defrosting.

2. Refrigerating apparatus including refrigerant liquefying means and refrigerant evaporating means, a thermostatic expansion valve including a thermostat bulb for controlling the flow of refrigerant from the liquefying means to the evaporating means for bringing the evaporating means below water freezing temperatures, fan means for circulating air over the surfaces of said evaporating means, and thermostatic means responsive to a low temperature for stopping the fan means, and having means for heating the thermostat bulb to r ,en wide the expansion valvefor unrestricted flow of uid fromthe liquefying means to the evaporating means coincidentally to the stopping of the fan means to raise the temperature of the evaporating means above freezing for defrosting and responsive to a high temperature for starting said fan fying means and refrigerant evaporating means, a thermo- 5 static expansion valve including a thermostat bulb for con trolling the fiow of refrigerant from the liquefying means to the evaporating means for bringing the evaporating means below water freezing temperatures, an electrically operated fan means for circulating air into heat transfer 10 relation with said evaporating means, an electric heater in heat transfer relation with said thermostat bulb, a double throw switch means connected to said fan means and heater having one position for energizing said fan means and deenergizing said electric heater for normal 15 refrigeration and having a second position for deenergizing said fan means and energizing said heater to open Wide said expansion valve to defrost said evaporating means, and thermostatic means responsive to a high temperature for moving said switch means to said one posi- 20 tion and responsive to a low temperature for operating said switch means to said second position.

4. Refrigerating apparatus including electrically operated refrigerant liquefying means and refrigerant evaporating means, a thermostatic expansion valve including a thermostat bulb for controlling the flow of refrigerant from the liquefying means to the evaporating means for bringing the evaporating means below water freezing temperatures, an electrically operated fan means for circulating air into heat transfer relation with said evaporating means, an electric heater in heat transfer relation with said thermostat bulb, a double pole double throw switch means having one position energizing said liquefying means and said fan means for normal refrigeration and a second position deenergizing said fan means and energizing said electric heater .to open wide said expansion valve for defrosting said evaporating means, and means responsive to the temperature of said evaporating means for deenergizing said electric heater.

References Cited in the file of this patent UNITED STATES PATENTS 

